The laser has been used since 1983 for interstitial heating of biological tissue. In the meantime, various probes and applicators have been developed to irradiate laser light into human tissue. Corresponding devices are described in German patent applications open to public inspection 38 13 227, 41 37 983, 42 13 053 and 42 21 364.
The previously described systems are constructed according to one more or less similar principle. The laser light is launched into an optical element located in the tip of the waveguide through a waveguide. Here as a rule it is a question of mirrors or prisms as well as special diffusers which permit an even irradiation of the laser light in all directions of space. These systems are provided in part with a cooling circuit for an additional modification of the temperature area profile, as this is, for example, described in DE-A-42 21 364, from which the preamble of claim 1 proceeds. A main problem of all interstitial heating procedures is, however, the exact adaptation of the temperature area profiles to the given tissue lesion. This will be sketched briefly with reference to the example of prostatic hyperplasia.
The prostate is divided anatomically into a right and a left prostate lobe as well as a median lobe. The geometrical extension is indeed similar in a normal prostate, apart from differences in size. The intensities of pathological changes are, however, extraordinarily different from patient to patient. In addition to a general enlargement of the prostate, there are also found isolated changes in the right or left prostate lobes as well as in the median lobe. Moreover, of course, very different combinations of these pathological changes can occur in individual cases. In addition to this, it frequently results that the target tissue reacts differently to laser radiation although the irradiation profile was adapted to the lesion. The temperature distribution can thus assume undesirably excessively high or, however, even too low temperatures during the irradiation. A similar problem emerges in connection with irregularly formed tumors, whereby especially the histological composition within the tumor (living cells, necroses, hemorrhages, vessels) can supervene in an aggravating manner. A laser probe which solves this problem has not been described until now.